1. Field of the Invention
The invention relates to a baby walker, more particularly to a movable base for a baby walker.
2. Description of the Related Art
Referring to FIG. 1, a conventional height-adjustable baby walker 1 is shown to comprise a movable base with a looped base frame 10, a tubular frame 11, a top frame 12 and a seat portion 13. The base frame 10 is formed as an oval loop with an inverted U-shaped cross-section. The movable base further includes a plurality of universal casters 14 provided on the base frame 10 to permit movement of the base frame 10. Usually, about four casters 14 are mounted on the base frame 10 to ensure stability of the latter. The tubular frame 11 includes a spaced pair of tubular slide rails 111 which have two ends secured to an inner wall surface of the base frame 10 and which extend adjacent to respective opposite longer side walls of the base frame 10. The tubular frame 11 further includes a pair of U-shaped tubes 112, 113. The distal ends of a first one of the U-shaped tubes 112 are fixed to one of the ends of the slide rails 111 and are connected to the base frame 10. Each of the distal ends of a second one of the U-shaped tubes 113 is provided with a slide seat 114 that is movable slidably along a respective one of the slide rails 111. The vertical arms of the U-shaped tubes 112, 113 cross one another and are connected pivotally by means of a pivot joint 115. The top frame 12 is formed with an oval hole 121 and a tray 122 on a front side of the hole 121. The tray 122 has a bottom side that is supported on a horizontal portion of the first U-shaped tube 112. The seat portion 13 is secured on the top frame 12 and is suspended on two sides of the hole 121.
In use, a baby is seated on the seat portion 13 such that his legs extend therethrough. The position of the slide seats 114 on the slide rails 111 is then adjusted in order to adjust correspondingly the height of the top frame 12, thereby permitting the feet of the baby to rest firmly on the floor. The universal casters 14 permit movement of the baby walker 1 in any direction on the floor. When the baby becomes tired, his feet cease to rest firmly on the floor and his weight is supported by the seat portion 13, thereby permitting the baby to take a nap.
Note that the conventional baby walker 1 is dangerous to use when the floor is inclined. When the baby's feet cease to rest firmly on the floor, free rolling of the casters 14 occurs. This may result in overturning of the baby walker 1, thereby resulting in injuries to the baby.
In order to overcome this drawback, retractable spring-loaded casters, such as those disclosed in U.S. Pat. Nos. 2,613,389, 3,096,536, 3,216,048, 3,216,049 and 5,001,808, have been used to replace the universal casters 14. These casters generally comprise a tubular sleeve with a bottom end that is provided with a shield, and a wheel, such as a ball wheel, disposed in the sleeve and biased by a spring so as to be retractable within the shield. The shield may be cup-shaped or cylindrical-shaped. The spring may be a coil spring or a bellows tube, as taught in U.S. Pat. Nos. 2,995,355 and 4,740,005.
When the feet of a baby seated on a conventional baby walker, which incorporates the spring-loaded casters, cease to rest firmly on the floor, the tubular sleeve of each caster moves downward and compresses the spring so that the lowermost edge of the shield contacts the floor to minimize free-rolling of the casters. Free-rolling of the casters, however, can still occur sometimes because the lowermost edge of the shield is smooth. Furthermore, it is also noted that these casters are relatively complicated in construction.
In a further modification of the conventional baby walker, suction cup units may be used with casters, as disclosed in U.S. Pat. No. 2,945,242, in order to grip the floor so as to anchor the baby walker. Thus, when the weight of a baby is applied on a conventional baby walker which incorporates the spring-loaded casters and at least one suction cup unit, the suction cup unit grips the floor when the shield of the casters contacts the latter. However, when the weight of the baby is removed from the baby walker, the expansion force of the spring is sometimes insufficient to overcome the suction force of the suction cup unit, thereby hindering movement of the baby using the baby walker.
It is also noted that when the conventional baby walker is used on an uneven floor surface, such as on a staircase, it is possible that one of the casters will cease to contact the floor if the baby walker was used carelessly, thereby causing the baby walker and the baby seated thereon to fall down the staircase.
Although baby walkers with anti-tipping devices, such as those disclosed in U.S. Pat. Nos. 2,765,839, 4,166,516 and 4,699,392 and in Norwegian Patent No. 91045, are known in the art, such devices are generally complicated in construction and provide inadequate protection to prevent toppling of the baby walker when used carelessly on a staircase.